This invention relates to a worn lining indicator for disc brake friction pads.
Continued operation of a motor vehicle after the friction lining of a disc brake friction pad has worn to a relatively thin level may be quite dangerous in view of the incipient failed condition of the vehicle brakes and may also be quite expensive, since contact of unlined metal with the rotor may severely damage the latter, requiring its replacement. Consequently, it is desirable to provide some sort of visual or audible warning when the friction lining on the disc brake friction pad has worn to a relatively thin thickness. Such a warning device must be relatively simple, both to assure that it may be manufactured at a minimum cost, and also because complicated brake lining wear indicators are subject to failure themselves. However, if the worn lining indicator produces an audible warning, the audible warning must be loud enough and distinctive enough so that the vehicle operator will recognize the warning and be able to distinguish it from the normal brake and road noises. One type of brake lining wear indicator provides a vibrating reed which is carried on a base which is attached to the backing plate of the friction pad. When the lining has worn to a relatively thin level, the vibrating reed engages the friction face of the rotor, which vibrates the reed and thereby causes a relatively loud noise which warns the vehicle operator of the worn condition of the brake linings. However, to assure proper operation of this worn lining indicator, the axis of the reed must engage the friction face of the rotor along a radius of the lining to produce the loudest possible noise. It has been necessary, in attaching the warning device to the backing plate, to use complicated and expensive fixtures to position the warning device in its proper position relative to the backing plate. However, use of such fixtures greatly increases the assembly cost of the friction pad assembly.